Cellular-ceramic process and apparatus



'June 12 1934. R POWELL v 1,963,031

I CELLULAR CERAMIC PROCESS AND APPARATUS Original Filed March 29, 1932 2 Sheets-Sheet l lLlUl Clay LlqUl Clay Liquid Cfay Llquld Clay U5 U6 v28 L29 m m g.1. Ea EU 1 v #3 r W V I7 F051 Mixi g L I9 20 2| Drying 32 Fasr Mixing 22 "-33 24 Burning-- 23Hea1'ing 37-25 *34'Coafinq manna.

INVENTOR.

June 12, 1934. E. R. POWELL CELLULAR CERAMIC PROCESS AND APPARATUS Original Filed March 29, 1952 2 Sheets-Sheet 2 Patented June 12, 1934 CELLULAR-CERAMIC PROCESS AND APPARATUS Edward 1:. Powell, Alexandria, ma.

Application March 29, 1932, Serial No. 601,795 Renewed January 30, 1934 11 Claims.

This invention relates to a cellular ceramic material.

It relates particularly to a ceramic building material in which there are air cells or air spaces,

5 the solid material or ceramic material proper comprising an expanded or cellular structure which encloses or nearly encloses these air cells.

This structure results from the principal features of the invention which comprise the formation of gas bubbles within the material while it is in wet liquid condition and the subsequent preservation of the bubbled or expanded stock thus formed until the material is finally dried and fired to the hard or vitrified condition which is characteristic of ceramic ware; such drying being of a character that it does not materially destroy the expanded structure previously imparted thereto. a

The advantages 01' a material of this type over solid brick or tile are: (1) Low shipping and handling weights which permit larger units and lighter foundations and framework. (2) Higher thermal resistance so that, when the material is built into walls, better heat barriers will be formed. (3) Adaptibility such as easier drilling and cutting and anchoring of screws and nails. (4) Better bonding of mortars on unglazed faces due to the open structure which permits the mortar to enter and bond. (5) Better acoustical properties when the cells are of the proper type and the cellular arrangement is exposed.

The cellular material has adensity of about 30 to 50 lbs. per cu. ft. as compared to 120 to 150 lbs. for solid ceramic material such as commercial brick or solid tile. The other differences in properties are related to and result from these differences in density and structure.

The principal object of the invention is to manufacture a material which has these advantages in a convenient and economical manner from any clay or shale which has fair plasticity when comminuted; and to do this without adding a large volume or percentage of combustible or volatile aggregate or setting reagents.

The chief feature of the invention consists in the accomplishment of this object by the use of certain processes and certain refinements oftechnique in the mixing of the clays and the relatively small amounts of chemicals so that a desired amount and desired type of expansion are obtained; and in the subsequent molding, drying and burning to produce the desired product without material destruction of the cellular arrangement. 56- The process includes (1) the preparation of two mutually chemically reactive'supplies of liquid clay in free flowing condition but without any unnecessary proportion of water; (2) the mixing of these two liquid clays in order to free a gas and sometimes to produce other desirable results more specifically set forth hereinafter; the mixing being at such a rate that it is intimate and substantially complete before the major part of the reaction has taken place; (3) the delivering of this mixture with a minimum of disturbance to a drier; (4) the exposing in the drier of a relatively large surface of the material in proportion to the volume and depth thereof; (5) the hardening of this material by heating in expanded condition so that it will not readily remix with water but is more or less water-absorbent; (6) the coating of the aggregate obtained from the last operation with more liquid reactive material as obtained from the second operation or other suitable binder to bond the material and finally molding into shapes.

There are, naturally, numerous conventional operations both before, between and after the above operations. These include mining or winning of the clay, grinding, tempering, trimming, separating into units, texturing, glazing, drying and burning. The invention, therefore, resides in the above mentioned operations, the apparatus therefor and the product therefrom taken in connection with the conventional. processes practised in other ceramic art.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a flow sheet showing the passage of the material through the process.

Fig. 2 is a diagrammatic layout of one form gt apparatus suitable for practising the inven- Fig. 3 is an enlarged plan of one form of continuous mixer, parts being shown in central section, said mixer being adapted to perform rapid continuous mixing.

Fig. 4 is an elevational view of another form of mixer for the same purpose as that-of Fig. 3, parts thereof being shown in central section.

Fig. 5 is a section through a structural unit of one. form of finished product which is provided with an lmperforate surface coating.

Fig. 6 is a similar view. through another form of finished product which is provided with a perforate coating.

Referring to Fig. 1, the two supplies of liquid clay 11 and 12 are withdrawn at 15 and 16 respectively and delivered to the fast mixing operation at 1'7, the amount being regulated as at 13 and 14 respectively. The mixture is dried at 19, and 21; is transferred at 22 to the heating operation at 23. A, burning operation at 24 supplies heat which is utilized in the heating operation at 23 and subsequently utilized in the drying operation and finally discharged at 38. The two supplies of liquid clay 26 and 27 are similarly withdrawn at 28 and 29,. 30 and 31, like 13 and 14, representing the step of feeding measured amounts of the clay; Heated aggregate 23 is measured andsized at 37-25. Liquid clays mixed at 32 are delivered at 33 and combined in the form of a coating on the aggregate at 34. The coated or mixed material is withdrawn at 35 and passes to the molding operation at 36 where it is formed and sized to shape. The resulting mass is then dried, trimmed or separated into units if necessary and fired as in other ceramic processes.

The preparation of the liquid clay may require more grinding than ordinarily practised in brick making. This extra grinding may be done wet or dry. The ground clay is mixed with water and tempered to the right consistency.

A satisfactory formula for the clay in the liquid clay supply 11 may include 7 per cent finely powdered dolomite and 1 per cent soda ash based on the dry weight of the clay; and that for the clay in the liquid clay supply 12 may include 2 per cent sulphuric acid, the extract from 1 per cent of soap bark and A per cent of karaya gum. The acid reacts with the dolomite and the soda ash to form carbon dioxide in the form of bubbles. The soap bark has the effect of preserving the bubbles and the karaya gum stabilizes the froth temporarily.

The amount of clay from supply 12 may be less in proportion to that from supply 11. A clay of the colloidal type which is in deflocculated condition when acid is preferable for the material of clay supply 12. The liquid clays should both be initially in deflocculated condition so that a minimum of water is required to keep them liquid, agitation of some sort often being required. The resulting mixture should preferably be fiocculated, to hold the structure until dried. For this condition, the mixture should usually be nearly neutral or slightly acid. The above example is for a carbonate-containing clay slip adapted to react with an acidulated clay slip. Other acids andcarbonates may be used. Also other reactions such as caustic with zinc or aluminum dust may be employed.

The dried material usually crumbles easily arid will break up in a rotary kiln to the desired size. If it is too large for the size slab to be molded, it may be crushed. It may be advisable to mold the material in large slabs, and separate into smaller or thinner units while green. For some purposes the ware may be molded to size and shape in a manner similar to wet mud brick making and need not be trimmed.

For minimum density in the completed product, the bonding matetrial should preferably be expanded also, as represented by the fast mixing at 32.

For a "marble-ized effect, the clays in the aggregate may burn to a different colorfrom those of the bonding material. If the product is dressed or split and left uncoated, this eflect will show in the finished product.

If desired, the reaction between the reactive liquid clays 11 and 12 or 26 and 27 may be so. regulated (by their temperature and composiin the pipes.

(J tion) that very little froth is formed until the mixture encounters the elevated temperature at 19-20-21; or at 34 where the mixture from 32 may encounter a hot or warm aggregate.

An example of apparatus suitable for practising the invention is shown .in Figs. 2, 3 and 4. The clay supplies 11, 12, 26 and 27 may be in tanks of conventional type. They may require agitation by mechanical stirrers 66, or air agitation or circulation may be used. The pipes 15, 16, 28 and 35 29 should be large. As a safety measure, they should be provided with water supplies for back washing to prevent clogging if the clay settles The above being standard practise, the apparatus is not shown. The feeding devices 14, 13, 30 and 31 may be gear pumps in which the clearances are larger than the particle size of the clay. Both impellers of the pumps should preferably be externally driven, so that they will not contact in the presence of the clay. This avoids excessive wear if the clay is abrasive. It is advisable to have the speeds of these feeding devices controllable.

A satisfactory form of fast continuous mixer 17 and 32 is shown in Fig. 3. It consists of a motor 40 which drives a rotor 47 by means of a shaft 45. A casing 42 is se ed by a gland 43 and houses the rotor. The casin has passages 44 and 41 for admitting the supplies of liquid clay. The clay is fed in by pressure and passes between the rotor and easing as the rotor revolves. The slightly conical passage 48 is small so that the clay passes through the mixer in a very short time. The speed of the rotor is such that the two supplies are intimately mixed by the time they reach the outlet 46. The slight conical formation is for subsequent adjustment for wear and for adjustment according to the consistency of the material to be handled.

Another form of mixer is shown in Fig. 4. In this form, the two supplies of clay liquid are discharged at considerable velocity from two nozzles 50 and 51. They meet at 52 and form a mixed stream. To complete the mixing, the mingled stream is deflected by inclined stationary vanes 54 and 55, which are opposite-disposed, and by forwardly inclined vane 53. By this method, the mixing is so rapid that the reaction is just starting when the material reaches the position 56. The reaction proceeds rapidly thereafter forming the frothed condition indicated at position 57. The approximate enlargement resulting therefrom is indicated clearly in Fig. 4.

The clay flows from mixer 17 down chute 18 into conveyor 19. Ordinarily the clay is liquid enough to spreaditself on .the conveyor. If not, it may be spread by hand or mechanically to a thin layer or into small wads. The conveyor'19, oven 20, baffles 21 and chutes 18 and 22 may all be of conventional type. Recirculation may be 135 used in oven 20 to increase the air velocity. Kiln 23 and crusher 65 may be of conventional type. A commercial feeder 25 is provided as an outlet for bin 37. Fuel burner 24 indicates any convenient fuel burning apparatus. The fan in connection with the oil supply 67 forms an oil flame for generating heat. Powdered coal, gas or solid fuel may also be used. The tumbler type mixer 34 is similar to a concrete mixer, and includes a regular charging chute 33. The mixing may be continuous or in batches. The molds 36 .represent any form of mold desired. Removable forms on a turn table are often used for this service.

' Fig. 5 represents a form of .finished product which may be made by this process. For gen eral structural purposes, an imperforate washable coating 58 is desirable and the cells 61 in the aggregate and cells 60 in the binding medium are mainly self-contained or separate individual bubbles enclosed in walls of ceramic material.

. This structure is desirable for strength.

Fig. 6 represents another form of product in which the structure is very open, having reentrant cells 63 and 64, cracks and honeycomb structure. This structure is obtained byexpanding the clay slips more than their surface tension will permit, thus rupturing the cellular structure. Also using insufficient bonding material-to fill the voids in the aggregate tends to form such a structure. A material of this sort has, in general, less structural strength than that shown inFig. 5 but has higher absorption of sound. Any coating such as 62 which is applied to a sound absorbing material should not be imperforate.

The ware may be any size or shape and may be used as part of any building structure. Except for a little calcium sulphate, a trace of sodium sulphate formed in thereaction and a trace of organic matter, the latter representing the soap bark and gum residue, there are usually no foreign materials present in the green ware. The burning of the product is,therefore, dependent largely on the characteristics of the original clay used. The final product contains nothing except material of ceramic character.

The details of the process and apparatus may be varied considerably without departing from the spirit of the invention. The above description should therefore be taken as illustrative and not in a limiting sense, the scope of the invention being defined by the appended claims.

The invention claimed is:

1. A process for making cellular ceramic ware including preparing two mutually reactive clay slips, mixing same to form a frothed structure molding into units in which this structure is embodied, drying and burning the ware in frothed condition.

2. A process for forming cellular ceramic ware including mixing a plurality of reactive clay slips with each other at a rate substantially greater than their speed of reaction-to form a product which has a frothed structure molding into units in which this structure is embodied, drying and burning the product.

3. A process for forming cellular ceramic ware which includes mixing chemical frothing agents with wet liquid clay, dividing the clay to expose a relatively large surface to an elevated temperature to bring about a reaction molding the resulting material into units which have a frothed structure, drying and burning the product.

4. A process for forming cellular ceramic ware which includes heating a dried expanded clay material to form an absorbent relatively nonmiscible aggregate, coating the aggregate with binding material, depositing the coated and expanded material in a form and allowing to set to form an expanded product, drying and burning same.

5. A process for forming a cellular ceramic material which comprises forming an acidulated slip, a carbonate-containing slip, mixing the two at a speed substantially greater than their speed of reaction to form a frothed slip and drying in such a manner as to preserve the resulting structure.

6. A process for forming cellular ceramic ware comprising expanding liquid clay, drying and hardening the clay in expanded condition to form a hardened absorbent aggregate, bonding the aggregate with more liquid clay, molding into units, drying and burning.

7. A process for forming cellular ceramic ware which includes forming a plurality of reactive clay slips which contain clay in relatively deflocculated condition, mixing and heating to form a frothed structure employing frothed material thus formed to mold an expanded unit, drying and hardening the product.

8. A process for manufacturing cellular ceramic ware comprising expanding clay in wet liquid condition, drying relatively rapidly in relatively distributed condition, heating to form an absorbent hardened aggregate, bonding with additional liquid clay, molding drying and burning the product.

9. Aprocess for forming cellular ceramic ware which comprises forming an expanded hardened aggregate of clay,'mixing with frothed clay to bond the aggregate to set the froth, molding into units drying trimming and burning to form a permanent material.

10. A process for forming cellular ceramic ware which includes forming a frothed clay slip, dry- 120 ing same rapidly to form a cellular aggregate, remixing with other clay which burns to a different color, molding into slabs, trimming to expose the expanded structure and burning to form a plurality of colors on the trimmed surface.

11. An apparatus for forming expanded ceramic ware including a plurality of clayslip feeding devices, a plurality of passages into a mixing device, means for rapid continuous mix ing and means for dehydrating the product.

EDWARD R. POWELL.- 

